1. Field of the Invention
In general, the present invention relates to counterbalance systems for windows that use coil springs to prevent open window sashes from moving under the force of their own weight. More particularly, the present invention system relates to systems and methods used to anchor a coil spring in the guide track of a tilt-in window.
2. Description of the Prior Art
There are many types and styles of windows. One of the most common types of windows is the double-hung window. Double-hung windows are the window of choice for most home construction. A double-hung window consists of an upper window sash and a lower window sash. Either the upper window sash or the lower window sash can be selectively opened and closed by a person sliding the sash up and down within the window frame.
A popular variation of the double-hung window is the tilt-in, double-hung window. Tilt-in, double-hung windows have sashes that can be selectively moved up and down. Additionally, the sashes can be selectively tilted into the home so that the exterior of the sashes can be cleaned from within the home.
The sash of a double-hung window has a weight that depends upon the materials used to make the window sash and the size of the window sash. Since the sashes of a double-hung window are free to move up and down within the frame of a window, some counterbalancing system must be used to prevent the window sashes from always moving to the bottom of the window frame under the force of their own weight.
For many years, counterbalance weights were hung next to the window frame in weight wells. The weights were attached to the window sash using a string or chain that passed over a pulley at the top of the window frame. The weights counterbalanced the weight of the window sashes. As such, when the sashes were moved in the window frame, they had a neutral weight and friction would hold them in place.
The use of weight wells, however, prevents insulation from being packed tightly around a window frame. Furthermore, the use of counterbalance weights on chains or strings cannot be adapted well to tilt-in, double-hung windows. Accordingly, as tilt-in windows were being designed, alternative counterbalance systems were developed that were contained within the confines of the window frame and did not interfere with the tilt action of the tilt-in windows.
Modern tilt-in, double-hung windows are primarily manufactured in one of two ways. There are vinyl frame windows and wooden frame windows. In the window manufacturing industry, different types of counterbalance systems are traditionally used for vinyl frame windows and for wooden frame windows. The present invention is mainly concerned with the structure of vinyl frame windows. As such, the prior art concerning vinyl frame windows is herein addressed.
Vinyl frame, tilt-in, double-hung windows are typically manufactured with guide tracks along the inside of the window frame. Brake shoe assemblies, commonly known as “shoes” in the window industry, are placed in the guide tracks and ride up and down within the guide tracks. The shoes are connected to coil springs that provide the counterbalance force. The coil springs are anchored to the guide tracks so that the coil springs unwind and rewind as the window sash moves up and down.
Coil springs are coiled ribbons of spring steel that have a free end. The coil springs resist the unwinding of the coiled ribbon and the separation of the free end of the spring from the remaining coiled body. In certain models of tilt-in windows, the wound body of the coil spring is mounted in a fixed position in the guide track of the window. The free end of the coil spring is connected to the brake shoe. In this manner, the coil spring resists any movement of the brake shoe away from the body of the coil spring. The coil spring is often held in a housing, wherein the housing is connected with mounting screws to the guide track. Often, a mounting screw passes through the center of the coil spring and acts as the pivot around which the coil spring rotates. If the mounting screw loosens or otherwise breaks free, the coil spring falls out of place and the window assembly must be repaired. Accordingly, strong well-set mounting screws are typically used. However, if a mounting screw is over-tightened, it may hamper the ability of the coil spring to rewind. This is especially true with certain models of tilt-in windows that have uneven surfaces within the guide track. If a mounting screw is over-tightened, it causes the housing to conform to the uneven surface of the guide track surface to which it is attached. This warps the housing and causes contact friction that inhibits the coil spring. Such prior art spring mounting assemblies are exemplified by U.S. Pat. No. 6,584,644 to Braid, entitled Spring Mounting For Sash Window Tensioning Arrangements.
When a person lifts a window sash to its open position, the ribbons of the coil springs rewind. The coil spring must be able to rewind in the short period of time that it takes to lift open the window sash. If the ability of a coil spring to rewind is hampered, the rewind rate of that coil spring may be longer than it takes to lift open a window sash. When this occurs, the ribbon of the coil spring is compressed between the slowly rewinding coil and the upwardly advancing sash. This causes the ribbon of the coil spring to snake and bend. It also prevents the window sash from opening. If the sash is forced open, the ribbon may kink. The ribbon will then never properly rewind and the window must be repaired before it will again work properly.
A need therefore exists for a coil spring mounting system that anchors a coil spring in place, yet cannot restrict the ability of the coil spring to both unwind and rewind. This need is met by the present invention as described and claimed below.